A. Field of the Invention
The claimed invention relates to the improvement of the nutritive value of soybean meal and other vegetable seed proteinaceous meals for feeding to ruminant animals. More particularly, the invention is concerned with improved meal compositions in which the protein content of the meal is protected from degradation within the rumen of the consuming animal, and the method for producing such meal compositions.
B. Related Art
It has been recognized for some time that the feeding values of some protein-providing feed materials are deleteriously altered by degradation in the rumen of ruminant animals. As a result of such rumen-degradation, the amount of protein that is ultimately available for metabolism by the feeding animal is diminished. It has therefore been considered advantageous to "protect" the protein component of the ruminant feed against being solubilized or metabolized in the rumen, allowing it to pass through in substantially undegraded form. The undegraded protein is thus available for digestion in the post-rumen portion of the feeding animal's digestive system.
With reference to feeding value lost by rumen destruction, soybean meal has a relatively low protein efficiency value. See Klopfenstein, Feedstuffs, Jul., 1981, 23-24. Since soybean meal is one of the major protein-containing feed materials used with ruminants, it is particularly desirable to provide a commercially practical means for protecting soybean meal against rumen destruction. For large scale commercial use such a method must be simple, efficient, and of relatively low cost. Such a method should thus be capable of being integrated into existing commercial facilities for processing soybeans and the like into feed materials.
A number of approaches have previously been pursued in attempts to protect the protein component of ruminant feeds. For instance, U.S. Pat. No. 3,619,200 proposes the application to a vegetable meal or other proteinaceous ruminant feed material of a rumen resistant coating. The purpose of the coating is to protect the proteinaceous feed from microbial attack in the rumen, followed by the decomposition of the coating in order to allow digestion of the feed within the abomasum and small intestine.
It has also been known that the solubility of protein in ruminant feed materials can be reduced by treating the feed materials with tannin, formaldehyde, or other aldehydes. In addition, a reduction of protein solubility can be obtained by heating the protein. These procedures are summarized with literature references thereto in U.S. Pat. No. 4,186,213. Feed materials that may be treated by one or more of these procedures to reduce the solubility of the protein in the rumen and to protect against rumen destruction are disclosed as including various vegetable meals.
Other prior art references of interest are:
Hudson et al. (1970), J. Anim. Sci., 30:609-613 PA1 Tagari et al. (1982), Brit. J. Nutr., 16, 237-243 PA1 Anderson, U.S. Pat. No. 3,463,858 (1969) PA1 Emery et al., U.S. Pat. No. 2,295,643 (1942) PA1 Ashmead, U.S. Pat. No. 4,172,072 (1979) PA1 Meyer, U.S. Pat. No. 4,664,905 (1987)
Hudson et al. describes an experimental comparison in lambs of postruminal nitrogen utilization of commercial soybean meal (72% N soluble) with meal heated 4 hours at 140.degree. C. (35% N soluble). The results suggest that the heated meal was degraded at a slower rate by ruminal microorganisms.
Tagari et al. compared solvent extracted soybean meals of different heat exposures. These included room temperature solvent removal, solvent removal at 80 .degree. C. for 10 minutes, and commercial toasted meal steamed at 120.degree. C. for 15 minutes. The meals were fed to rams and rumen liquor samples were tested. Artificial rumen comparisons for ammonia liberation were also made. It was concluded that the main factor determining the different efficiencies of process to non-process soybean meals is their different solubility in rumen liquor. It was also observed that changes in solubility caused by different heat treatments of soybean meal are relatively large in comparison with other meals.
Of particular interest with respect to the present invention are those methods and compositions involving the addition of zinc or other such substances to feed materials. Anderson discloses a procedure for preparing a growth factor for feeding domestic animals and poultry. A zinc salt in aqueous solution, such as zinc chloride or zinc sulfate, is reacted with free amino acids in a proteinaceous feed material. The reaction is carried out in an aqueous solution at a temperature of 60.degree.-70.degree. C. (140.degree.-158.degree. F.), and a pH of 3.5, which pH is said to be achieved automatically with ZnCl.sub.2, an adjustment of pH with HCl being used with other zinc salts. The reaction mixture is dried to a moisture content of 2-8%, and mixed with the feed ration. There is no reference to the feeding of ruminants, or to rumen protection of protein.
Emery et al. describes a process in which mineral compounds including zinc and other polyvalent metal oxides, hydroxides, and salts are reacted with proteinaceous feed materials in the presence of water and a protein splitting acid such as H.sub.3 PO.sub.4, HCl, or H.sub.2 SO.sub.4. The reacted mixture is dried by heating in air. Soybean meal is indicated as the preferred feed material and zinc is among the metals referred to for use in the form of oxides, hydroxides, or carbonates. Other salts, such as cobalt, are indicated as being used in the form of chlorides or sulfates. The examples illustrate the reaction of large amounts of the metal compounds with soybean meal (Ex. I, 35% and Ex. III 17%, based on the meal). There is no reference in this patent to either rumen protection or nutritional value.
Ashmead proposes the use of metal proteinates for supplying mineral deficiencies in humans and animals. The proteinates are prepared by reacting bivalent metal salts at an alkaline pH with free amino acids of enzyme-hydrolyzed proteins.
Meyer, in U.S. Pat. No. 4,664,905, discloses the addition of zinc to proteinaceous feeds, with the zinc being added in an aqueous solution or in a dry mix with subsequent steaming. The concentration of zinc ions is required to be in the range of 0.25-1.3% by weight, based on the dry weight of the meal.
While industry has previously recognized the use of zinc as an agent for protecting the protein content of vegetable feeds and the like, certain drawbacks have also become associated with its use. Most notably, concerns have been raised regarding the excretion of heavy metals such as zinc into the environment in animal manure.
In response to these concerns, countries throughout the world have enacted regulatory limitations on the maximum allowable levels of zinc in proteinaceous feed meals. Thus, a need has arisen for a feed composition, and a method for producing such a composition, that provides favorable rumen-bypass characteristics while incorporating low levels of zinc relative to compositions that are currently used.
It is also highly desirable for such a process to be either easily integrated into an existing facility for processing soybeans and the like, or even more advantageously, to be capable of being carried out at a remote site, such as a cattle feeding lot, without the need for large-scale equipment.
It is thus an object of the claimed invention to provide a protected feed composition that provides favorable rumen-bypass characteristics while incorporating relatively low levels of zinc.
It is a further object of this invention to provide a method for producing such protected feed compositions that can be easily incorporated into existing commercial facilities for processing soybeans and the like, or that can be carried out at a remote site.